Undergraduate Review. Jessica Sousa. Volume 4 Article 13
|
|
- Marybeth Lawrence
- 5 years ago
- Views:
Transcription
1 Undergraduate Review Volume 4 Article Kinematic Analysis of Mylonitic Rocks, Southern Ruby Mountains, SW Montana: Evidence for Proterozoic Orogenic Crustal Thickening and Topographic Collapse Jessica Sousa Follow this and additional works at: Part of the Earth Sciences Commons Recommended Citation Sousa, Jessica (2008). Kinematic Analysis of Mylonitic Rocks, Southern Ruby Mountains, SW Montana: Evidence for Proterozoic Orogenic Crustal Thickening and Topographic Collapse. Undergraduate Review, 4, Available at: This item is available as part of Virtual Commons, the open-access institutional repository of Bridgewater State University, Bridgewater, Massachusetts. Copyright 2008 Jessica Sousa
2 5 7 Jessica is a senior Earth Science major who conducted her research under the mentorship of Dr. Michael Krol with funding from an Adrian Tinsley program summer grant. Kinematic Analysis of Mylonitic Rocks, Southern Ruby Mountains, SW Montana: Evidence for Proterozoic Orogenic Crustal Thickening and Topographic Collapse Jessica Sousa Abstract Mylonitic granitic rocks from a large shear zone within the southern Ruby Mountains in southwest Montana record evidence for a multiple tectonic movement history. The shear zone is 500 meters thick with ductile shear fabrics generally striking northeast and dipping to the northwest. Foliations in the adjacent country rocks are sub-parallel to the foliations within the mylonites suggesting shear zone development was contemporaneous with the regional deformation and metamorphism of the country rock. A well-developed mineral stretching lineation, defined by aligned sillimanite crystals, records predominantly dipslip movement, but locally, oblique-slip is also preserved. Sheath-type folds developed in thin calc-silicate layers in calcitic marble have axial orientations similar to the down-dip mineral stretching lineations of the shear zones. Mesoscopic and microscopic analysis of the mylonites reveals the presence of asymmetric kinematic indicators that record a strong top-to-the-south sense of shear associated with regional compression, thrusting, and crustal thickening. However, in places an opposite shear sense can be identified indicating a period of top-to-the-north sense of shear corresponding with extension, normal faulting, and crustal thinning. The thrust episode is consistent with tectonic shortening and associated high-grade metamorphism reaching C and 7-11 kb. Normal movement appears to postdate thrusting, suggesting either a period of post-orogenic collapse due to topographic collapse resulting from an overthickened metamorphic pile (which can be seen today in the Himalayas) or a discretely younger tectonic event. However, the high temperature minerals that define the mineral lineation suggest they were closely related temporally. The timing of deformation, metamorphism, and mylonite formation in this area is unknown, although regional tectonic arguments suggest that highgrade metamorphism is associated with the Proterozoic, Ga Big Sky Orogeny. Introduction Recent studies, north of the Ruby range, in the Tobacco Root Mountains (e.g. Burger et al., 2004; Harms et al., 2004) has revealed geologic evidence for a Proterozoic tectonic event termed the Big Sky Orogeny that occurred 1.78 to 1.71 Ga. The Big Sky Orogeny was associated with collisional tectonics and high-grade metamorphism. The goal of this project is to study the kinematic BRID GEWATER STATE COLLEGE
3 5 8 history of mylonitic rocks in an effort to unravel a portion of the tectonic history affecting the southern portion of the Ruby Mountains in southwestern Montana. Asymmetric kinematic indicators allow for the determination of the sense of movement in ductile shear zones and provide information on the nature of tectonism that affected this region. In addition, metamorphic mineral assemblages in the ductile shear zones and adjacent country rocks yield information on the P-T conditions during the development of the ductile shear zone. Our work will provide a better understanding of the nature of tectonic activity in this part of southwest Montana in Proterozoic time. A modern analog similar to the results obtained in this study is found in the Himalayas of Pakistan and Nepal. Continued continental collision between the Indian and Eurasian plates resulted in the formation of numerous thrust faults and subsequent high-standing topography. The South Tibetan detachment, which is a large-scale normal fault, developed in response to the gravitational instability due to the overthickened crust (Burchfiel et al., 1992). Normal motion within the Himalayan orogen continues today even though it is within an overall compressional tectonic environment. Background The Ruby Mountains are one of several Archean-aged (2.7 Ga) metamorphic and igneous basement-cored uplifts exposed during Late Cretaceous-Tertiary time (Tysdal, 1981). The range extends approximately 60 km along its northeast trend and 20 km across in an east-west direction. The Ruby Mountains occur along the northwestern margin of the Wyoming province. Rocks in the Ruby and Tobacco mountains are believed to have been subsequently metamorphosed about billion years ago during an event known as the Big Sky Orogeny (Harms et al., 2004a; 2004b). This event was first described as affecting rocks in the Tobacco Root Mountains to the north but most likely extends into the Ruby Mountains to the south (Burger et al, 2004; Harms et al., 2004a). Several different lithologic units are present throughout the study area. These include; 1) biotite and hornblende gneisses, 2) calcitic-dolomitic marble, 3) amphibolite, 4) sillimanite-pelitic schists and gneisses, 5) quartzites, 6) banded iron formation, and 7) granitic and leucogranitic mylonite gneiss (Garihan, 1979; Karasevich et al., 1981). In addition, several small (10 s-100 m) isolated bodies of ultramafic rock intrude the metamorphic sequence and locally result in contact metamorphism and partial melting of adjacent country rock (Alcock et al., 2006). Our study concentrated on granitic mylonites interlayered in sequences of calcitic marble and amphibolite. Meso-Microscopic Observations Field work conducted in the Ruby Mountains involved geologic mapping, structural analysis, and sample collection of mylonitic rocks that occur near the crest of the southern portion of the Ruby range. We were able to differentiate several distinctive lithologic units in the study area including; 1) calcitic-dolomitic marble, 2) biotite and hornblende gneiss, 3) amphibolite, 4) sillimanite pelitic schist, 5) quartzite and 6) granitic and leucogranite mylonites. Isolated pods of ultramafic rock occur as m wide bodies intruding a variety of the metamorphic units. Understanding the regional-scale structural relationships is part of on-going research performed by Dr. Krol and his colleague from SUNY-Oneonta. Asymmetric kinematic indicators (Passchier and Simpson, 1996) were used to decipher the movement directions of mylonitic rocks in the ductile shear zone. The first outcrop examined was a sequence of interlayered calcitic marble and leucogranitic mylonite gneiss (Figure 1). The gneiss contains a strongly mylonitic texture, whereas the marble displays highly contorted and folded calc-silicate layers. The leucogranitic mylonite occur as layers about one meter thick within the encompassing marble layers. The mylonitic foliation strikes N67E and dips 50 NW. A mineral stretching lineation in the mylonite trends due north, and plunges 47 N. Kinematic indicators in the mylonite zone show a strong top-to-the-south or reverse sense of movement in the field. Mineral assemblages in the adjacent marble include calcite, diopside, and graphite. The folded calc-silicate layers of the marble found in this area have axial orientations that are sub-parallel to the lineation in the mylonite. However, their orientations are difficult to measure in the field. To the east are alternating layers of calcitic marble and more granitic mylonite outcrops (EG-56-07; Figure 2). The mylonite has a foliation striking N70E and dips 40 NW. A mineral lineation trends N15E and plunges 38 N. Kinematic indicators in the form of σ-porphyroclasts reveal oblique top-to-the-south sense (reverse) movement. The mylonite possesses a mineral assemblage which includes; quartz, K-feldspar, biotite, garnet, and kyanite. Kyanite is sub-parallel to the mineral lineation in the mylonite. Structurally below this zone shearing appears to intensify with the development of a stronger, more well-defined foliation. The foliation changes slightly with a strike of N60E and dip of 35 NW and a mineral lineation of N10E, plunging 24 N. Station EG-2-07s consists of calcite-diopside-biotite marble intruded by an undeformed granitic pegmatite. The marble contains calc-silicate layers that appear much less deformed as previously observed and the pegmatite also shows sign of minor deformation and no effects of mylonitization. However, to the east the pegmatite becomes weakly mylonitized. Also found at T H E U N D E R G R A D U AT E R E V I E W
4 5 9 this location are layers of amphibolite which appears to display a mylonitic fabric. The amphibolite has a foliation striking N78E and is dipping 36 NW. Approximately 1.5 km to the northwest and structurally above the marble unit is station EG-4-07s. The rocks here are dominated by a thick sequence of amphibolite (~7-8 m) interlayered with m thick layers of granitic mylonite (Figure 3a). The amphibolite also displays a mylonitic texture as well. Foliations strike N60E and dip 35 NW. These rocks also display a welldeveloped lineation with a trend of N5E, plunging 35 N, which is similar to the orientation observed in the granitic mylonites. The leucogranitic layers contain large, sheared kyanite crystals. Kyanite porphyroclasts are asymmetric and provide evidence for top-to-the north (normal) sense of shear (Figure 3b). Structurally above the layered amphibolite is a unit of finergrained, gray hornblende gneiss. The hornblende gneiss also displays the effects of mylonitization showing an oblique, topto-the-north movement sense (Figure 4). The foliation strikes N65E and dips 35 NW with mineral lineations trending N20E and plunging 30 N. Metamorphic Conditions Petrographic analysis of mylonitic rocks reveal mineral assemblages that include; quartz + microcline + plagioclase + garnet ± muscovite ± sillimantite ± kyanite ± biotite (Figure 7). This assemblage is characteristic and indicative of high-grade metamorphism in the upper amphibolite to lower granulite facies. Sillimanite needles and kyanite define the mineral lineation in some of the granitic mylonite indicating they grew contemporaneous with regional deformation and metamorphism. Mineral assemblages indicate P-T conditions reached 7-11 kb and C (Figure 8). Discussion Several conclusions can be made based upon the field and petrographic observations. Previous work proposed that the mylonites represented several discrete shear zones within a metamorphic sequence of amphibolite, pelitic schist, and calcite marble (Olsen et al., 2007). However, geologic mapping and kinematic analysis during the summer of 2007 indicate the zone of ductile shearing may actually encompass a much broader zone of deformation rather than concentrated along a series of discrete and distinct zones restricted to the granite and leucogranite mylonites. The highly deformed nature of the marble units and the presence of sheath folds with axes subparallel to the mylonitic foliation suggest the two are closely related and developed during the same tectonic event(s). Given the rheological and mechanical contrasts between marble and granitic mylonites and similar nature of deformation experienced by these units, we argue that the zone of movement must be accommodated over a larger, structurally thicker zone and not along thin, isolated zones of highly concentrated shear. The presence of kyanite and sillimanite, which define the mineral lineation, suggests that the tectonic event responsible for the formation of the ductile shear zones was associated with highgrade metamorphism with pressures of 7-11 kb and temperatures of C. The alignment of the sillimanite grains that define the lineation in the granitic mylonite shows that high-grade metamorphism was coeval with ductile shearing and is not an older relict mineral assemblage. The question that still remains is the timing of ductile shearing and the relationship between the two movement episodes as it relates to regional tectonism. The intriguing observation in the Ruby Mountain shear zones is the preservation of both thrust and normal movement in the same zone. Based upon those observations a two phase tectonic model is developed (Figure 9). The first phase of this model coincides with a time of regional compression creating reverse movement and crustal thickening, some of which was accommodated by the zone of ductile deformation. The second phase of this model represents a period of normal movement within these same zones. This sequence of events is also believed to be the most likely relative age of these two events. One possible explanation for the change from reverse movement to normal movement is in effect, gravity. The compressional phase resulted in an overly thickened crust that ultimately becomes gravitationally and topographically unstable. Therefore, a change in the regional stress field resulted in a change from reverse movement to a normal sense of motion. A modern-day analogue can be seen in the Himalayan Mountains of Pakistan and Nepal (Burchfiel et al., 1992; Krol et al., 1997; Dougherty et al., 1998). There have been several normal faults identified within the mountain range, the most extensive being the South Tibetan Detachment System (Burchfiel et al., 1992). These normal faults have been identified as being contemporaneous with thrusting at depth. Burchfiel et al. (1992) concluded this was due to collapse of high-standing topography driven by gravity. So while shortening was occurring at deeper crustal levels in an overall compressive stress regime, crustal extension was occurring synchronous at higher crustal levels. The result is a mid-crustal wedge that exposes rocks that show both thrust movement at the bottom and extensional movement at the top. Another possibility for the multiple directions of movement within the same shear zone is the idea that as granitic magma was intruded into the calcitic marble and amphibolite units it thermally weakened the crust resulting in the topographic collapse. Aoya et al. (2005) concluded, based upon U-Pb dating and 40 Ar- 39 Ar dating, that the emplacement of a granitic pluton BRID GEWATER STATE COLLEGE
5 6 0 occurred at the time of the Himalayan Orogeny. He concluded that a transition took place from compressional to extensional movement the same time this pluton intruded, suggesting this was the driving force behind the collapse. This collapse would have caused decompression melting and additional intrusions of granitic magmas, further weakening the overlying crust. Conclusions It remains unclear which scenario caused the nearly simultaneous extensional and compressional movement within the ductile shear zone in the southern portion of the Ruby Mountains. This area was initially thought to consist of several small, discrete ductile shear zones restricted to the granitic mylonites, however, recent work suggests the zone of ductile deformation is distributed across a much wider zone. Asymmetric kinematic indicators reveal a predominantly top-to-the-south sense of movement that coincides with regional compression. A transition from reverse (top-to-the-south) to normal movement (top-to-the north) developed in response to gravitational collapse of high topography or collapse driven by thermal weakening of the crust due to granitic intrusions. Additional work is required to distinguish between these possibilities. Figure 1. Granitic mylonite outcrop within a sequence of calcitic marble, Elk Gulch quadrangle. View to the east (hammer for scale). Foliation dips to the north (left). Figure 2. Granitic mylonite interlayered within calcitic marble (pencil for scale). Metamorphism of the granitic mylonites and adjacent country rocks indicate pressure and temperatures of 7-11 kb and C, respectively. Ductile shearing was coeval with high-grade metamorphism as shown by the alignment of sillimanite needles parallel to the shearing lineation. Based upon regional correlations and similarities with rocks in the Tobacco Root Mountains north of the Ruby range, the shearing event is believed to be linked with the Big Sky Orogeny which took place during the early Proterozoic 1.78 to 1.71 Ga. Acknowledgements I would like to thank Dr. Michael Krol for his help and support throughout this process and for giving me this wonderful opportunity. We are extremely grateful to the Adrian Tinsley Program for the financial and personal support that allowed this research to be carried out. Special thanks to co-coordinators Anne Brunjes and Peter Saccocia. Dr. Krol would also like to acknowledge the Center for Advancement for Research & Teaching at Bridgewater State College for supporting various aspects of his research in Montana. T H E U N D E R G R A D U AT E R E V I E W
6 61 Figure 3. A) Dark layered amphibolite with thin light colored granitic mylonite zones. The overall shear sense is top-to-thenorth. Jess Sousa for scale. B) close-up of asymmetric kyanite (ky) porphyoclast and boudinaged and sheared felsic layer showing top-to-the-north sense of shear. Figure 4. σ-type porphyroclast of feldspar showing top-tothe-north sense of shear. Montana quarter for scale. -type A Figure 5. Photomicrograph of a σ-type feldspar (Fsp) porphyroclast showing top-to-the-north shear sense in a granitic mylonite. Field of view 2 mm. N S σ-type B B R I D G E WAT E R S TAT E C O L L E G E
7 6 2 Figure 6. Equal-area stereographic projection of metamorphic and mylonitic fabric elements. Note tight clustering of mineral lineations plunging north. Figure 8. P-T grid showing mineral assemblages and possible P-T conditions during ductile shearing. Gray box shows P-T range of mylonitic rocks. Figure 7. Photomicrograph of sillimanite crystals defining the mineral lineation. Plane polarized light, field of view 4 mm. Figure 9. Proposed tectonic model for the development and subsequent collapse of the Ruby Mountains during the Ga Big Sky Orogeny. Ruby Mtns Stage I: Compressional Pre-1.8 Ga (?) Big Sky Orogeny T H E U N D E R G R A D U AT E R E V I E W
8 6 3 References Alcock, J, Muller, P.D., and Krol, M.A., 2006, Contact Metamorphism adjacent to the Paleoproterozoic Wolf Creek Ultramafics, southern Ruby Range, SW Montana, Evidence for Magmatic : Geological Society of America Abstracts with Programs, Vol. 38, p Aoya, M., Wallis, S. R., Terada, K., Lee, J., Kawakami, T., Wang, Y., and Heizler, M., 2005, North-South Extension in the Tibetan Crust Triggered by Granite Emplacement : Geological Society of America: Geology, v. 33, p Burchfiel, B. C., Zhihliang, C., Hodges, K. V., Yuping, L., Royden, L. H., Changrong, D., and Jiene, X., 1992, The south Tibetan detachment system, Himalayan orogen: extension contemporaneous with and parallel to shortening in a collisional mountain belt : Geological Society of America Special Paper 269, p Burger, H. R., 2004, General geology and tectonic setting of the Tobacco Root Mountains : Geological Society of America Special Paper 377, p Dougherty, A., Krol, M., & Hodges, K., 1998, Miocene tectonic unroofing and cooling of the Greater Himalayan sequence, Nyalam region, southern Tibet : Geological Society of America Abstracts with Programs, v. 30, p Garihan, John M., 1979, Geology and Structure of the Central Ruby Range, Madison County, Montana: Summary : Geological Society of America Bulletin, Part 1, v. 90. p Harms, T. A., Burger, H. R., Blednick, D. G., Cooper, J. M., King, J. T., Owen, D. R., Lowell, J., Sincock, M. J., Kranenburg, S. R., Pufall, A., and Picornell, C. M., 2004a. Character and origin of Precambrian fabrics and structures in the Tobacco Root Mountains, Montana : Geological Society of America Special Paper 377, p Harms, T. A., Brady, J. B., Burger, H. R., and Cheney, J. T., 2004b, Advances in the geology of the Tobacco Root Mountains, Montana, and their implications for the history of the northern Wyoming province : Geological Society of America Special Paper 377, p Karasevich, L. P., Garihan, J. M., Dahl P.S., and Okuma, A. F. 1981, Summary of Precambrian Metamorphic and Structural History, Ruby Range, Southwest Montana : Montana Geological Society Field Conf. p Krol, M.A., Sherwood, M., & Dougherty, A., 1999, Tertiary denudation history of the Indian plate, Naran, Pakistan: Constraints from 40Ar/39Ar thermochronology, Geological Society of America Abstracts with Programs, v. 31, p. 29. Olsen, R. L., Krol, M. A., Muller, P. D., and Alcock, J., 2007, Preliminary Kinematic Analysis of Mylonite Zones within the Southern Ruby Mountains, SW Montana: Implications for Regional Proterozoic(?) Tectonic, Geological Society of America Abstracts with Programs, Vol. 39, p. 74 Passchier, C. W., and Simpson, C., 1986, Porphyroclast System as Kinematic Indicators : Journal of Structural Geology, v. 8, p Tysdal, Russell G., 1981, Foreland Deformation in the Northern Part of the Ruby Range of Southwestern Montana : Montana Geological Society Field Conference, p BRID GEWATER STATE COLLEGE
Chapter 8 Lecture. Earth: An Introduction to Physical Geology. Twelfth Edition. Metamorphism. Rocks. Tarbuck and Lutgens Pearson Education, Inc.
Chapter 8 Lecture Earth: An Introduction to Physical Geology Twelfth Edition Metamorphism and dmetamorphic Rocks Tarbuck and Lutgens Chapter 8 Metamorphic Rocks What Is Metamorphism? Metamorphism means
More informationReport of Activities 2003 Published by: Manitoba Industry, Economic Development and Mines Manitoba Geological Survey, 2003.
Report of Activities 2003 Published by: Manitoba Industry, Economic Development and Mines Manitoba Geological Survey, 2003. ERRATA: The publisher/department name in the bibliographic reference cited immediately
More informationLisa Gaston NMT. Photo courtesy of Mike Williams. Matt Heizler
Lisa Gaston NMT Photo courtesy of Mike Williams Matt Heizler Precambrian Geology Field Area 40 Ar/ 39 Ar results Do the pegmatites record intrusion ages? Conclusions Future work Precambrian provinces of
More informationLOW GRADE PRECAMBRIAN ROCKS OF THE CENTRAL GRAVELLY RANGE, SW MONTANA
LOW GRADE PRECAMBRIA ROCKS OF THE CETRAL GRAVELLY RAGE, SW MOTAA ELIZABETH KLEI Amherst College Sponsor: Tekla Harms and Jack Cheney ITRODUCTIO Laramide uplift of the southern Gravelly Range of southwestern
More informationMETAMORPHISM OF PRECAMBRIAN ROCKS IN THE SOUTHERN HIGHLAND MOUNTAINS, SOUTHWESTERN MONTANA
METAMORPHISM OF PRECAMBRIAN ROCKS IN THE SOUTHERN HIGHLAND MOUNTAINS, SOUTHWESTERN MONTANA JESSICA A. MATTHEWS Amherst College Sponsor: John T. Cheney INTRODUCTION A diverse Precambrian sequence of garnetrich
More informationIsan deformation, magmatism and extensional kinematics in the Western Fold Belt of the Mount Isa Inlier
Isan deformation, magmatism and extensional kinematics in the Western Fold Belt of the Mount Isa Inlier Rick Gordon Department of Earth Sciences University of Queensland A thesis submitted for examination
More informationMetamorphic Energy Flow. Categories of Metamorphism. Inherited Protolith Character. Inherited Fabric. Chemical Composition
Metamorphic Energy Flow Categories of Metamorphism Best, Chapter 10 Metamorphic processes are endothermic They absorb heat and mechanical energy Absorption of heat in orogenic belts Causes growth of mineral
More information2 Britain s oldest rocks: remnants of
Britain s oldest rocks: remnants of Archaean crust 15 2 Britain s oldest rocks: remnants of Archaean crust 2.1 Introduction Owing to the complex nature of extremely old deformed rocks, the standard methods
More informationLecture 5 Sedimentary rocks Recap+ continued. and Metamorphic rocks!
Lecture 5 Sedimentary rocks Recap+ continued and Metamorphic rocks! Metamorphism Process that leads to changes in: Mineralogy Texture Sometimes chemical composition Metamorphic rocks are produced from
More information610 C. DAVIDSON ET AL. thermal structure at a given instant in time. In-sequence thrusting may result in the propagation of top to the south shearing across the MCTZ and into the footwall of the MCT, thereby
More informationGEOLOGIC MAPS PART II
EARTH AND ENVIRONMENT THROUGH TIME LABORATORY - EES 1005 LABORATORY FIVE GEOLOGIC MAPS PART II Introduction Geologic maps of orogenic belts are much more complex than maps of the stable interior. Just
More informationMetamorphism: summary in haiku form
Metamorphism & Metamorphic Rocks Earth, Chapter 8 Metamorphism: summary in haiku form Shape-shifters in crust. Just add heat and/or pressure. Keep it solid please! What Is Metamorphism? Metamorphism means
More informationAppendix A2: Detailed description of all results
Appendix A2: Detailed description of all results This Appendix presents detailed descriptions of all results in this study. It is presented separately in order to streamline the main paper, and to provide
More information"When Gregor Samsa woke up one morning from unsettling dreams, he found himself changed into a monstrous bug. Metamorphosis, by Franz Kafka
Metamorphosis "When Gregor Samsa woke up one morning from unsettling dreams, he found himself changed into a monstrous bug. Metamorphosis, by Franz Kafka Metamorphism The transformation of rock by temperature
More informationCHAPTER 3.3: METAMORPHIC ROCKS
CHAPTER 3.3: METAMORPHIC ROCKS Introduction Metamorphism - the process of changes in texture and mineralogy of pre-existing rock due to changes in temperature and/or pressure. Metamorphic means change
More information6 Exhumation of the Grampian
73 6 Exhumation of the Grampian mountains 6.1 Introduction Section 5 discussed the collision of an island arc with the margin of Laurentia, which led to the formation of a major mountain belt, the Grampian
More informationRemapping the Six Mile Quadrangle
The 23rd Annual David S. Snipes/Clemson Hydrogeology Symposium Field Trip Guidebook Remapping the Six Mile Quadrangle Tallulah Falls Biotite Gneiss exposed on Mile Creek Shoals, Six Mile, SC Field Trip
More informationCHAPTER VI CONCLUSIONS
CHAPTER VI CONCLUSIONS In this Chapter, salient observations made in understanding the various tectonothermal events, including U-Pb in-situ monazite geochronology of Sargur schists and granulites exposed
More informationMetamorphism and Metamorphic Rocks
Page 1 of 13 EENS 1110 Tulane University Physical Geology Prof. Stephen A. Nelson Metamorphism and Metamorphic Rocks This page last updated on 25-Sep-2017 Definition of Metamorphism The word "Metamorphism"
More informationExtrusion as a mechanism of gneiss dome emplacement, Himalayan orogen: kinematic and vorticity analysis of Gianbul Dome, NW India
Extrusion as a mechanism of gneiss dome emplacement, Himalayan orogen: kinematic and vorticity analysis of Gianbul Dome, NW India By: Meilani Bowman-Kamaha o Advisor: Dr. Jeff Lee Committee Members: Dr.
More informationEESC 4701: Igneous and Metamorphic Petrology METAMORPHIC ROCKS LAB 8 HANDOUT
Sources: Caltech, Cornell, UCSC, TAMIU Introduction EESC 4701: Igneous and Metamorphic Petrology METAMORPHIC ROCKS LAB 8 HANDOUT Metamorphism is the process by which physical and chemical changes in a
More informationGEOLOGY OF THAILAND (METAMORPHIC ROCKS)
GEOLOGY OF THAILAND (METAMORPHIC ROCKS) High-Grade Metamorphic Rocks (Precambrian?) Low-Grade Metamorphic Rocks (Lower Paleozoic) 1 THAILAND EXPLANATION Lower Paleozoic Rocks (Low Grade) Precambrian (?)
More informationMetamorphic Petrology GLY 262 P-T-t paths
Metamorphic Petrology GLY 262 P-T-t paths Pressure-Temperature-Time (P-T-t) Paths The complete set of T-P conditions that a rock may experience during a metamorphic cycle from burial to metamorphism (and
More information12. MYRMEKITE IN THE SANTA ROSA MYLONITE ZONE, PALM SPRINGS, CALIFORNIA
1 ISSN 1526-5757 12. MYRMEKITE IN THE SANTA ROSA MYLONITE ZONE, PALM SPRINGS, CALIFORNIA Lorence G. Collins email: lorencec@sysmatrix.net February 15, 1997 Introduction Myrmekite, containing tiny quartz
More informationPractice Test Rocks and Minerals. Name. Page 1
Name Practice Test Rocks and Minerals 1. Which rock would be the best source of the mineral garnet? A) basalt B) limestone C) schist D) slate 2. Which mineral is mined for its iron content? A) hematite
More informationStrike-Slip Faults. ! Fault motion is parallel to the strike of the fault.
Strike-Slip Faults! Fault motion is parallel to the strike of the fault.! Usually vertical, no hanging-wall/footwall blocks.! Classified by the relative sense of motion. " Right lateral opposite block
More informationGeologic Structures. Changes in the shape and/or orientation of rocks in response to applied stress
Geologic Structures Changes in the shape and/or orientation of rocks in response to applied stress Figure 15.19 Can be as big as a breadbox Or much bigger than a breadbox Three basic types Fractures >>>
More informationChapter 15 Structures
Chapter 15 Structures Plummer/McGeary/Carlson (c) The McGraw-Hill Companies, Inc. TECTONIC FORCES AT WORK Stress & Strain Stress Strain Compressive stress Shortening strain Tensional stress stretching
More informationAppendix 11. Geology. of the. I60 area
Appendix 11 Geology of the I60 area 1. Locality The locality of the I60 area is as follows; Northwestern corner; UTM_EW 530513, UTM_NS 7345741 Southwestern corner; UTM_EW 530418, UTM_NS 7301454 Northeastern
More informationPreface and Overview. Folded strata in the mountains of Italy (ca AD), Leonardo da Vinci
Preface and Overview Folded strata in the mountains of Italy (ca. 1500 AD), Leonardo da Vinci Models of Mountain Building and Associated Deformation as represented by G.P. Scrope Deformation Feature: Scales
More informationIntroduction. Introduction. Introduction 10/15/2014. The Agents of Metamorphism. Metamorphism. and Metamorphic Rocks
Introduction Metamorphism The transformation of rocks, usually beneath Earth's surface, as the result of heat, pressure, and/or fluid activity, produces metamorphic rocks Metamorphism and Metamorphic Rocks
More informationLab 6: Metamorphic Rocks
Introduction The Earth s crust is in a constant state of change. For example, plutonic igneous rocks are exposed at the surface through uplift and erosion. Many minerals within igneous rocks are unstable
More informationIntroduction. Introduction. Chapter 7. Important Points: Metamorphism is driven by Earth s s internal heat
Chapter 7 Metamorphism and Metamorphic Rocks Introduction Metamorphism - The transformation of rocks, usually beneath Earth's surface, as the result of heat, pressure, and/or fluid activity, produces metamorphic
More informationMountain Building. Mountain Building
Mountain Building Mountain building has occurred during the recent geologic past American Cordillera the western margin of the Americas from Cape Horn to Alaska Includes the Andes and Rocky Mountains Alpine
More informationStructure and history of the Kern Canyon fault system: introduction and thesis overview
1 Chapter 1 Structure and history of the Kern Canyon fault system: introduction and thesis overview Exposures of fault zones from the surface to deep levels afford an opportunity to study the transition
More informationIntroduction to Geology Spring 2008
MIT OpenCourseWare http://ocw.mit.edu 12.001 Introduction to Geology Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. Regional metamorphism
More informationCopyright McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education
Copyright McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education Tibetan Plateau and Himalaya -southern Asia 11.00.a VE 10X
More informationThermobarometry of the Leo Pargil Dome, NW India: Insights into Exhumation of Mid-Crustal Rocks in the Himalaya
Pursuit - The Journal of Undergraduate Research at the University of Tennessee Volume 2 Issue 1 Spring 2011 Article 4 March 2011 Thermobarometry of the Leo Pargil Dome, NW India: Insights into Exhumation
More informationLab: Metamorphism: minerals, rocks and plate tectonics!
Introduction The Earth s crust is in a constant state of change. For example, plutonic igneous rocks are exposed at the surface through uplift and erosion. Many minerals within igneous rocks are unstable
More informationNew geologic mapping + and associated economic potential on northern Hall Peninsula, Baffin Island, Nunavut
New geologic mapping + and associated economic potential on northern Hall Peninsula, Baffin Island, Nunavut Holly Steenkamp, M.Sc. Regional Mapping Geoscientist David Mate, M.Sc. Chief Geologist November
More informationProf. Tejas S Patil Dept Of Geology M.J.College.
Prof. Tejas S Patil Dept Of Geology M.J.College. Metamorphic rocks When rocks are baked by heat of molten magma or squeezed by the movements of huge tectonic plates or by the pressure of overlying thick
More informationMetamorphic Rocks and the Rock Cycle
Petrology Session 3 Metamorphic Rocks and the Rock Cycle Presented by Dr. I Wayan Warmada warmada@gmail.com What are Rocks? Most rocks are an aggregate of one or more minerals, and a few rocks are composed
More informationMetamorphic Rocks. SWHS Geology
Metamorphic Rocks SWHS Geology What are they? From the greek roots meta (change) and morphos (form): Rocks that have been changed in form from the temperature, pressure, and fluids inside the earth. A
More informationEarth Science, (Tarbuck/Lutgens) Chapter 10: Mountain Building
Earth Science, (Tarbuck/Lutgens) Chapter 10: Mountain Building 1) A(n) fault has little or no vertical movements of the two blocks. A) stick slip B) oblique slip C) strike slip D) dip slip 2) In a(n) fault,
More informationChapter 10: Deformation and Mountain Building. Fig. 10.1
Chapter 10: Deformation and Mountain Building Fig. 10.1 OBJECTIVES Describe the processes of rock deformation and compare and contrast ductile and brittle behavior in rocks. Explain how strike and dip
More informationMetamorphism and metamorphic rocks. GEOL115 Alexander Lusk
Metamorphism and metamorphic rocks GEOL115 Alexander Lusk Outline: Metamorphic rocks Defini>on and major types of metamorphism Rock cycle Metamorphic processes Deforma>on and development of a folia>on/
More informationTerm 1 final review ES
Name: Date: 1. t what approximate altitude in the atmosphere can stratospheric ozone be found?. 10 km. 30 km. 70 km D. 100 km 2. What percentage of Earth s history represents human existence?. less than
More informationBig Island Field Trip
Big Island Field Trip Space Still Available Group Airline Tickets May be available if enough people sign on If interested send email to Greg Ravizza Planning Meeting Next Week Will
More informationFalmouth Town Landing, Falmouth, Maine
Maine Geologic Facts and Localities April, 2018 Falmouth Town Landing, Falmouth, Maine 43 o 43 57.2 N, 70 o 12 16.7 W Text by Ian Hillenbrand, Department of Agriculture, Conservation & Forestry 1 Photo
More informationGondwana Research 24 (2013) Contents lists available at ScienceDirect. Gondwana Research. journal homepage:
Gondwana Research 24 (2013) 1203 1222 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr Cratonic reactivation and orogeny: An example from the northern
More informationMetamorphic Petrology. Jen Parks ESC 310, x6999
Metamorphic Petrology Jen Parks ESC 310, x6999 jeparks@sciborg.uwaterloo.ca Definition of Metamorphism The IUGS-SCMR SCMR definition of metamorphism: Metamorphism is a subsolidus process leading to changes
More informationTECTONIC AND STRUCTURAL CONTROLS ON INTRUSION- RELATED DEPOSITS IN THE NORTHERN PART OF SREDNA GORA ZONE, BULGARIA NIKOLAY PETROV & KAMELIA NEDKOVA
TECTONIC AND STRUCTURAL CONTROLS ON INTRUSION- RELATED DEPOSITS IN THE NORTHERN PART OF SREDNA GORA ZONE, BULGARIA NIKOLAY PETROV & KAMELIA NEDKOVA INVESTIGATED AREA Praveshka Lakavica deposit Elatsite
More informationCrags, Cracks, and Crumples: Crustal Deformation and Mountain Building
Crags, Cracks, and Crumples: Crustal Deformation and Mountain Building Updated by: Rick Oches, Professor of Geology & Environmental Sciences Bentley University Waltham, Massachusetts Based on slides prepared
More informationTrip B-2 VARIATIONS IN L- AND S-TECTONITE ON THE NORTHERN BOUNARY OF THE PISECO LAKE SHEAR ZONE, ADIRONDACK MOUNTAINS, NEW YORK
Trip B-2 VARIATIONS IN L- AND S-TECTONITE ON THE NORTHERN BOUNARY OF THE PISECO LAKE SHEAR ZONE, ADIRONDACK MOUNTAINS, NEW YORK DAMIAN PIASCHYK 1, DAVID VALENTINO 2, GARY SOLAR 3, JEFFREY R. CHIARENZELLI
More informationMetamorphic fluids, Naxos, Greece
Field trip Naxos, Greece, course B, SS 2014: Prof. Dr. J. Urai Metamorphic fluids, Naxos, Greece Tilman Scheele Applied Geosciences EMR, RWTH Aachen Introduction Naxos is located in the central Aegean
More informationFaults, folds and mountain building
Faults, folds and mountain building Mountain belts Deformation Orogens (Oro = Greek all changes for mountain, in size, shape, genesis orientation, = Greek for or formation) position of a rock mass Structural
More informationChapter 8 10/19/2012. Introduction. Metamorphism. and Metamorphic Rocks. Introduction. Introduction. The Agents of Metamorphism
Chapter 8 Metamorphism Introduction Metamorphism - The transformation of rocks, usually beneath Earth's surface, as the result of heat, pressure, and/or fluid activity, produces metamorphic rocks During
More informationMetamorphism / Metamorphic Rocks
Metamorphism / Metamorphic Rocks Metamorphism: occurs when rocks are subjected to heat, pressure, and/or other environmental conditions - The rock remains a solid during this time period - Why Should You
More informationUnderstanding Earth Fifth Edition
Understanding Earth Fifth Edition Grotzinger Jordan Press Siever Chapter 6: METAMORPHISM Modification of Rocks by Temperature and Pressure Lecturer: H Mohammadzadeh Assistant professors, Department of
More informationIntroduction to Prospecting. Session Two Geology
Introduction to Prospecting Session Two Geology The Earth Earth is 4.6 billion years old (Ba). Bacteria & algae +3.5 Ba. Microscopic animals ~2 Ba. Animals ~600 million years (Ma) old. Mankind about 100,000
More informationTopics Laramide Orogeny: Late Cretaceous to Early Eocene Reading: GSA DNAG volume 3, Ch. 6
Topics Laramide Orogeny: Late Cretaceous to Early Eocene Reading: GSA DNAG volume 3, Ch. 6 Late Cretaceous to early Eocene New patterns developed 5 main regions Tectonic interpretations Post-Laramide events
More informationFINAL EXAM Crustal Deformation CONVERGE DIVERGENT PLATES MANTLE PLUMES FLUX BASALTIC GRANITIC
Crustal Deformation Reading: Chapter 10 Pages 283-304 Review Questions 4, 6, 7, 10, 12, 15, 18, 20 FINAL EXAM NOON TO 2 PM, TUESDAY DEC. 5 HERE: Natural Science 101 BRING A SCAN TRON TURN IN YOUR REVIEW
More informationDeformation of Rocks. Orientation of Deformed Rocks
Deformation of Rocks Folds and faults are geologic structures caused by deformation. Structural geology is the study of the deformation of rocks and its effects. Fig. 7.1 Orientation of Deformed Rocks
More informationMETAMORPHIC ROCKS CHAPTER 8
Lecture 6 October 18, 20, 23 October 19, 24 METAMORPHIC ROCKS CHAPTER 8 This is only an outline of the lecture. You will need to go to class to fill in the outline, although much of the relevant information
More informationMetamorphic Rocks. Metamorphic Rocks: Big Ideas
Metamorphic Rocks: Big Ideas Earth scientists use the structure, sequence, and properties of rocks to reconstruct events in Earth s history Earth s systems continually react to changing influences from
More informationMetamorphism (means changed form
Metamorphism (means changed form) is recrystallization without melting of a previously existing rock at depth in response to a change in the environment of temperature, pressure, and fluids. Common minerals
More informationGEOL FORENSIC GEOLOGY ROCK IDENTIFICATION
GEOL.2150 - FORENSIC GEOLOGY ROCK IDENTIFICATION Name I. Introduction There are three basic types of rocks - igneous, sedimentary, and metamorphic: Igneous. Igneous rocks have solidified from molten matter
More informationLecture 9 faults, folds and mountain building
Lecture 9 faults, folds and mountain building Rock deformation Deformation = all changes in size, shape, orientation, or position of a rock mass Structural geology is the study of rock deformation Deformation
More informationRocks and the Rock Cycle. Banded Iron Formation
Rocks and the Rock Cycle Banded Iron Formation Rocks Big rocks into pebbles, Pebbles into sand. I really hold a million, million Rocks here in my hand. Florence Parry Heide How do rocks change? How are
More informationNAME HOMEWORK ASSIGNMENT #3 MATERIAL COVERS CHAPTERS 8, 9, 10, 11
NAME HOMEWORK ASSIGNMENT #3 MATERIAL OVERS HAPTERS 8, 9, 10, 11 Assignment is due the beginning of the class period on November 23, 2004. Answers for each chapter will be discussed in class, as Exam #3
More informationReview - Unit 2 - Rocks and Minerals
Review - Unit 2 - Rocks and Minerals Base your answers to questions 1 and 2 on the diagram below, which shows the results of three different physical tests, A, B, and C, that were performed on a mineral.
More information16. Metamorphic Rocks II (p )
16. Metamorphic Rocks II (p. 233-242) Causes of Metamorphism The two main processes that occur within a rock during metamorphism are: : physical processes like squeezing and crushing - caused by strong
More informationStrength variation and deformational behavior in anisotropic granitic mylonites under high-temperature and -pressure conditions An experimental study
Strength variation and deformational behavior in anisotropic granitic mylonites under high-temperature and -pressure conditions An experimental study Gui Liu, Yongsheng Zhou, Yaolin Shi, Sheqiang Miao,
More informationPETROLOGY OF BANDED IRON FORMATION AND PHYLLITE IN THE STANDARD CREEK CONTACT AUREOLE, SOUTHERN GRAVELLY MOUNTAINS,
PETROLOGY OF BANDED IRON FORMATION AND PHYLLITE IN THE STANDARD CREEK CONTACT AUREOLE, SOUTHERN GRAVELLY MOUNTAINS, ALYSSA DOODY Smith College Sponsor: John Brady INTRODUCTION The Wyoming Province is an
More informationCenozoic Extensional Basin Development and Sedimentation in SW Montana
Cenozoic Extensional Basin Development and Sedimentation in SW Montana Robert C. Thomas Department of Environmental Sciences, The University of Montana Western, Dillon, MT 59725, (406) 683-7615, r_thomas@umwestern.edu
More informationCrustal Deformation Earth - Chapter Pearson Education, Inc.
Crustal Deformation Earth - Chapter 10 Structural Geology Structural geologists study the architecture and processes responsible for deformation of Earth s crust. A working knowledge of rock structures
More informationAnswers: Internal Processes and Structures (Isostasy)
Answers: Internal Processes and Structures (Isostasy) 1. Analyse the adjustment of the crust to changes in loads associated with volcanism, mountain building, erosion, and glaciation by using the concept
More informationFig. Captions. Fig. 1. Generalized geologic map of eastern Nepal after Akiba et al. (1973), Carosi et al. (1993b),
41 Fig. Captions Fig. 1. Generalized geologic map of eastern Nepal after Akiba et al. (1973), Carosi et al. (1993b), Lombardo et al. (1993), and our field interpretations. The upper left inset shows the
More informationWhat Causes Rock to Deform?
Crustal Deformation Earth, Chapter 10 Chapter 10 Crustal Deformation What Causes Rock to Deform? Deformation is a general term that refers to all changes in the shape or position of a rock body in response
More informationMetamorphic Petrology GLY 262 Metamorphism and plate tectonics
Metamorphic Petrology GLY 262 Metamorphism and plate tectonics Regional Metamorphism in a broad sense: metamorphism that affects a large body of rock, and thus covers a great lateral extent Three principal
More informationTECHNICAL REPORT: REGIONAL GEOLOGY AND TECTONICS Resume. Huachon Project, Cerro de Pasco departments, Peru. By: AFC Logistic SAC
TECHNICAL REPORT: REGIONAL GEOLOGY AND TECTONICS Resume Huachon Project, Cerro de Pasco departments, Peru By: AFC Logistic SAC December 2016 1. INTRODUCTION GPM Metals Peru, in its portfolio of generating
More informationEssentials of Geology, 11e
Essentials of Geology, 11e Crustal Deformation and Mountain Building Chapter 17 Instructor Jennifer Barson Spokane Falls Community College Geology 101 Stanley Hatfield Southwestern Illinois College Jennifer
More informationGlobal Tectonics. Kearey, Philip. Table of Contents ISBN-13: Historical perspective. 2. The interior of the Earth.
Global Tectonics Kearey, Philip ISBN-13: 9781405107778 Table of Contents Preface. Acknowledgments. 1. Historical perspective. 1.1 Continental drift. 1.2 Sea floor spreading and the birth of plate tectonics.
More informationWhich rock is shown? A) slate B) dunite C) gneiss D) quartzite
1. Which metamorphic rock will have visible mica crystals and a foliated texture? A) marble B) quartzite C) schist D) slate 2. The recrystallization of unmelted material under high temperature and pressure
More informationRR#7 - Multiple Choice
1. Which mineral is mined for its iron content? 1) hematite 2) fluorite 3) galena 4) talc 2. Which rock is composed of the mineral halite that formed when seawater evaporated? 1) limestone 2) dolostone
More informationGLY 155 Introduction to Physical Geology, W. Altermann. Press & Siever, compressive forces. Compressive forces cause folding and faulting.
Press & Siever, 1995 compressive forces Compressive forces cause folding and faulting. faults 1 Uplift is followed by erosion, which creates new horizontal surface. lava flows Volcanic eruptions cover
More informationHand specimen descriptions of metamorphic rocks
Hand specimen descriptions of metamorphic rocks Hand specimen descriptions for metamorphic rocks are like those for igneous rocks. The objective is to tell someone looking at it everything they need to
More informationMetamorphism: A Process of Change
Metamorphism: A Process of Change Updated by: Rick Oches, Professor of Geology & Environmental Sciences Bentley University Waltham, Massachusetts Based on slides prepared by: Ronald L. Parker, Senior Geologist
More informationMountains and Mountain Building: Chapter 11
Mountains and Mountain Building: Chapter 11 Objectives: 1)Explain how some of Earth s major mountain belts formed 2) Compare and contrast active and passive continental margins 3) Explain how compression,
More informationMountains are then built by deforming crust: Deformation & Mountain Building. Mountains form where stresses are high!
Deformation & Mountain Building Where are mountains located? Deformation and Folding Mountain building Mountains form where stresses are high! Mountains form at all three types of plate boundaries where
More informationCrustal Deformation. Earth Systems 3209
Crustal Deformation Earth Systems 3209 Crustal Deformation pg. 415 Refers to all changes in the original form and/or size of a rock body. May also produce changes in the location and orientation of rocks.
More informationAge (Ma) Age (Ma) Age (Ma)
8 Description of Mapped Units 113 ' 46 7.' 29 47 23 21 Tac Anaconda Beds - sediments and volcaniclastics 21 81 19 7 42 11 36 4 68 Kgd 69 8 84 69 8 2 7 22 19 22 49 68 79 89 6 82 21 69 71 79 82 77 9 84 36
More informationJonathan A. Nourse Department of Geological Sciences California State Polytechnic University Pomona, CA
Comparison of Late Cretaceous Plutonic Rocks Across the Left-Lateral San Antonio Canyon Fault, San Gabriel Mountains Daniel E. Heaton Department of Geological Sciences San Diego State University San Diego,
More informationRegional GIS based exploration targeting studies in data poor environments
Regional GIS based exploration targeting studies in data poor environments A case study of gold prospectivity mapping in Nigeria Matthew Greentree, Mathieu Lacorde and Bert De Waele Acknowledgements Australian
More informationMetamorphic Rock Origin and Identification
Metamorphic Rock Origin and Identification Physical Geology GEOL 101 Lab Ray Rector - Instructor http://www.rockhounds.com/rockshop/rockkey/index.html http://earthsci.org/education/teacher/basicgeol/meta/meta.html
More informationFactors cause Metamorphism:
Metamorphic Rocks: A rock whose original mineralogy, texture and/or composition has changed due to pressure, temperature and/or fluids. It can be formed from igneous, sedimentary, or previously metamorphosed
More informationAn Overview of Graphite Projects from Asia to Africa. Dr Mike Cunningham SRK Consulting (Australasia) Pty. Ltd.
An Overview of Graphite Projects from Asia to Africa Dr Mike Cunningham SRK Consulting (Australasia) Pty. Ltd. Acknowledgements PT. Granfindo Nusantara RS Mines Pty Ltd Geological Survey and Mining Bureau
More informationMetamorphism & Metamorphic Rocks
1 2 3 4 5 6 7 8 9 10 11 & Metamorphic Rocks Earth 9 th edition, Chapter 8 Mass wasting: summary in haiku form Shape-shifters in crust. Just add heat and/or pressure. Keep it solid please! Key Concepts
More informationAs compaction and cementation of these sediments eventually occur, which area will become siltstone? A) A B) B C) C D) D
1. A student obtains a cup of quartz sand from a beach. A saltwater solution is poured into the sand and allowed to evaporate. The mineral residue from the saltwater solution cements the sand grains together,
More informationGEOL Lab 11 (Metamorphic Rocks in Hand Sample and Thin Section)
GEOL 333 - Lab 11 (Metamorphic Rocks in Hand Sample and Thin Section) Introduction - Metamorphic rock forms from any pre-existing rock that undergoes changes due to intense heat and pressure without melting.
More information